fdw validation function vs zero catalog id

It appears that the function for validating generic options to a FDW,
SERVER and USER MAPPING is always passed a catalog oid of 0. Whereas
it should actually be passed the oid of the catalog that the options
apply to.

Attached patch fixes the issue by passing the proper catalog id from
transformGenericOptions().

PS. I personally would like this applied to 8.4 as well -- it'd enable
us to write a proper validator for pl/proxy fdw.

regards,
Martin